Roll-up venetian blind



Nov. '19, 1963 H. NELSON ROLL-UP VENETIAN BLIND 3 Sheets-Sheet 1 FiledJune 9, 1960 3 1 5 E C E 05 N Z 2 W 5M w v V I T N 9 w m Tr H 4 f// 7/0By Nov. 19, 1963 H. NELSON 3,111,163

ROLL-UP VENETIAN BLIND Filed June 9, 1960 3 Sheets-Sheet 2 V II mnua! II"all" llllllllillllplll.u".wlllpillllllllllllllll my:

VE'NT'OE: HAEEY NELSON,

BY Wad, n TOR/J Ks Nov. 19, 1963 H. NELSON ROLL-UP VENETIAN BLIND 3Sheets-Sheet 3 Filed June 9, 1960 6- MM Q 1 M E m w w. VY A we H I. a, 5

3,111,163 BULL-UP VENETIAN BLIND Harry Nelson, St. Louis, Mo assignor toArtcraft Venetian Blind Manufacturing Company of St. Louis, St. Louis,Mo, a corporation oi Missouri Filed June 9, 196 3, Ser. No. 35,048 6Elaims. (Q1. I6ll23) This invention relates to a blind structure andmore particularly to a blind that is raised and lowered by rotation ofthe member to which the blind is attached.

There are two types of blinds generally available at the present time.One is the type that is raised and lowered by pulling a cord and openedand closed by pulling another cord. The other is a roll-up blind orshade that rolls from the bottom. The latter type may not be opened andclosed by varying the angle of the slats. Both types when raised producea bunching of the slats at the lower end. In the one type mentioned,this bunch ing results when the lowermost slats are raised againstsuccessive ones of themselves. In the other type mentioned, the bunchingresults because the roll is produced by rolling the blind from thebottom.

The blind of the present invention combines all the features desired ina blind. It can be opened to admit light and air or can be closed toachieve privacy. It can be raised and lowered by rolling, but withcomplete absence of a visible bundle or bunching because it is rolledfrom the top. In short, the blind is one that comprises tiltable slatsthat can be rolled up in much the same way as a window shade. The abovesets forth a primary object of the invention.

Conventional Venetian blinds have separate means for raising andlowering the blind from the means that causes the blind to open andclose. The present blind performs functions similar to theseconventional blinds, that is, the blind of the instant invention can beraised and lowered and the slats that make up the blind can be pivotedbetween horizontal or open and vertical or closed positions. One of thefeatures of the invention that is quite ditlerent from the conventionalblind so that both the raising and lowering of the blind and opening andclosing of the blind are accomplished by a single operating means. Thisdiiierence is one of the principal objects of the invention. It meansthat the blind does not require the conventional types of hardwareneeded for tilting the slats.

An important object of the invention is to provide a means for raisingand lowering the blind and is locked without requiring any additionalmanipulation of a pull cord other than to release it. In conventionalVenetian blinds the cord that raises and lowers the blind must be swungover to a toothed catch before the blind is locked in place. In thepresent invention, the locking means operates automatically upon releaseof the pull cord.

Another object of the invention is to provide a Venetian blind that issuspended from a rotatable member with a cord for rotating the memberand thereby for raising and lowering the blind, wherein the weight ofthe blind provides part of the means for locking the cord againstcounterrevolution after it has been rotated in a blind raisingdirection.

Still another object of the invention is to provide a Venetian blindhaving a plurality of slats suspended from a rotatable member by verythin cord means and wherein the slats are of narrow and thinconstruction, so that when the slats are pivoted to a horizontal or openposition, both the slats and the cord means that suspend the slats willprovide a relatively unobstructed view through a window opening.

Still another object of the invention is to provide a atent i iceVenetian blind suspended by a rotatable member, wherein the blindcomprises a plurality of slats that can be pivoted between a horizontalor open position and a vertical or closed position and the blind can beraised or lowered by rotating the member from which it is suspended andwherein there is a single means for both openin and closing the blindand raising or lowering the blind.

Another important object of the invention is to provide a Venetian blindthat is adaptable to being mounted above an opening in a building inpairs, with one blind being suspended from a rotatable element with aspace between the uppermost part of the blind and the rotatable elementwhen the blind is fully lowered, and wherein the other blind issuspended from an element with little or no space between the uppermostpart of the blind and its rotatable element so that when both blinds arelowered, the lower part of the building opening will be covered by oneof the blinds and the upper part by the other blind, whereby the pair ofblinds may be used in a variety of decorative ways including thepresentation of a cafe curtain eliect.

Yet another object of the invention is to provide a Venetian blindsuspended from a rotatable element wherein the element is releasablyattached to bracket means mounted to a wall surface.

In the drawings:

FIGURE 1 is a front elevation view of the Venetian blind with the blindfully lowered;

FIGURE 2 is a front elevation view of the Venetian blind with the blindhalfway lowered;

FIGURE 3 is a partial front elevation view with the blind completelyraised;

FIGURE 4 is a partial enlarged front elevation view of the top portionof the Venetian blind with the cover removed and the blind fullylowered;

FIGURE 5 is a view similar to that of FIGURE 4 but with the blindpartially raised;

FIGURE 6 is a view similar to FIGURE 4, but with the blind rolled allthe way up;

FIGURE 7 is a greatly enlarged view taken along the line 7-7 of FIGURE1;

FIGURE 8 is a greatly enlarged view taken along the line 8-8 of FIGURE1;

FIGURE 9 is a view in section and partially broken away, taken along theline 99 of FIGURE 7;

FIGURE 10 is a view in section taken along the line Iii1il of FIGURE 9;

FIGURE 11 is a View in Ill-ll of FIGURE 9;

FIGURE 12 is a view in 12-12 of FIGURE 9;

FIGURE 13 is a view in 131l3 of FIGURE 12;

FIGURE 14 is a partial view taken from the left end of FIGURE 9, outwith the cover plate removed to show the mechanism of the locking meansfor the Venetian blinds;

FIGURE 15 is a side view of the pulley;

FIGURE 16 is a top view of a cover plate;

FIGURE 17 is a side elevation view of the cover plate of FIGURE 16;

FIGURE 18 is a typical, transverse cross-section through the Venetianblind with the blind completely lowered;

FIGURE 19 is a view similar to FIGURE 18 but after a slight rotation hasbeen imparted to the drum;

FIGURE 20 is a view in section similar to FIGURE 18 wherein the drum hasbeen further rotated;

FIGURE 21 is a partial view of the top portion of the Venetian blindshowing a modified form of the means for attaching the Venetian blind tothe drum;

FIGURES 22 through 28 represent a modified form of section taken alongthe line section taken along the line section taken along the line 3 theinvention with particular emphasis on different structure for the meansfor rotating the drum;

FIGURE 22 is an enlarged partial view in section of the left end of theVenetian blind;

FIGURE 23 is a view in section taken along the line 2323 of FIGURE 22;

FIGURE 24 is a view in section taken along the line 2424 of FIGURE 23;

FIGURE 25 is a view in section through the drum show ing the way thepull-cords are attached;

FIGURE 26 is a view of the locking clip for the cord;

FIGURE 27 is a view in section taken along the line 27-27 of FIGURE 26;

FIGURE 28 is an enlarged end view of the cord-retaining clip of FIGURE26 taken from the right side of FIG- URE 26 showing the clip before ithas been bent around a cord;

FIGURES 29 through 33 represent a particular embodiment of the inventionwherein two of the Venetian blinds are mounted in generally superposedrelationship so that a cafe curtain effect can be obtained;

FIGURE 29 is a front elevation view showing both Venetian blinds all theWay down;

FIGURE 30 is a partial front elevation view showing the upper Venetianblind all the way down;

FIGURE 31 is a front elevation view showing the lower Venetian blind allthe way down and the upper Venetian blind all the way up;

FIGURE 32 is a partial front elevation view showing the lower Venetianblind all the way down and the upper Venetian blind part of the waydown; and

FIGURE 33 is an end view of the double Venetian blind arrangementshowing the relationship between the superposed Venetian blind.

Referring now to the drawings, FIGURE 1 shows the assembled Venetianblind 39 mounted to a suitable surface 31 by a cover structure 32. Thecover structure includes two side cover plates 33 and 34 attached byscrews 35' to the surface 31. Each of the side plates 33 has a rear edge36, a bottom edge 37 perpendicular to the rear edge and a curved surface38 joining the top of the rear edge 36 and the outward end of the bottomedge 37.

An elongated and curved front cover plate 39 conceals the edges 38 ofthe end plates 33 and 34 and is attached by screws 40 to inturnedflanges 41 of the end plates 33 and 34-.

Each of the plates 33 and 34 has suitable mounting means formed in itfor supporting the Venetian blind. The plate 33 has a hole 45 throughit, and rotatably fastened to the hole by means of a rivet 46 is apulley 47. There is a bearing washer 48 between the pulley 47 and theplate 33. The pulley 47 has an outwardly directed hook 49 toward itsperiphery, and opposite to the hook 4-9 is a pin 50.

The supporting member for the Venetian blind comprises a hollow drum orcylinder 54. The open ends of the cylinder or drum 54 are covered byflanged caps 55 and 56, the flanges of which are inserted into thehollow drum 54. The end cap 55 has a pair of holes 57 through it. Theopposite end cap 56 has a stud 53 attached to its center, the stud 58having a head '59 on it. The end cap 34 has an inwardly extending boss6% that has a key slot 61 through its center. Thus, the drum 54 issecured between the end plates 33 and 34 by first hooking one hole 57onto the hook 49, then pivoting the drum 54- until the pin '50 passesthrough the other hole 57, and thereafter sliding the stud '58 intolocking engagement with the key slot 61. When so mounted, the drum 54can freely rotate between the plates 33 and 34.

The blind itself comprises a plurality of very thin slats 65 which arepreferably formed of a suitable metal and grooved slightly. The slatsdiffer from the conventional Venetian blind slats in that they have amaximum width of approximately one inch. And furthermore, when theslats, as a group, are viewed edgewise, as they might be viewed by onelooking through an open blind and through a window, they are barelyvisible. The fact that they are painted white adds to the effect. Thereare certain features of the present invention that do not dependprimarily upon the size, shape or color of the slats, but the importanceof this description will be apparent when other aspects are described.

here are a plurality of cords 66-, 67 and 63 wrapped about the drum 54and taped by a suit-able tape 69 at the drum. However, the free ends7t), 71 of the cords 66, (57 and 6 a depend from the drum 54 in pairsspaced apart by a distance approximately equal to the width of the slats65.

Between each pair of free ends 7% land 71 is attached a cord 72, andfrom the middle of the cord 72 with respect to the end cords 66 and 68,there hangs a cor-d 73. There are a number of short cords 74 attachedbetween the free ends 7% and 71 of each cord 66, 67 and 68. The shortpieces 74 are spaced vertically by the distance it is intended to spacethe slats 65. All of the cords are very thin, braided nylon, preferablywhite in color so that they will be practically invisible in sunlight.

When each of the cord ends 76 and 71 is hanging directly vertically fromthe drum 54, as illustrated in FIG- URE 18, the cords will behorizontal. Then when the drum is rotated in a manner to be described asillustrated in FIGURES 19 and 20", one of the cord ends 79 or 71 will beraised first thereby interrupting the horizontal position of the shortpieces 74.

Each of the slats '65 has :a transverse elongated aperture 77 through itadjacent each of its ends in as many places as there are cords 66, 67and 63, and these apertures 77 are intended to permit the center cord 73to pass through them. Thus, each slat is supported upon the severalshort cord pieces 7 4 that lie in the same horizontal plane, and thecenter vertical cords 73 adjacent each side of the blind pass througheach of the apertures 77 to keep the slats 65 from slidinglongitudinally. At the bottom of the blind is a single thicker slat 73to which all the vertical cord pieces 73, 71 and 73 are attached.

A heavier cord makes almost :a complete revolution about the pulley 47.The free ends 85 and 87 of the cord 85 hang below the pulley. It ispreferable that the cord 85 be a continuous loop, although such is notrequired.

There are a pair of guide blocks 83 and 89 attached by screws 96} to aplate to be described. The guide blocks 38 and 89 have inner ends 91 and92 that are spaced apart a distance slightly greater than twice thethickness of the cord 85. The upper surfaces 33 and 94 of the blocks 83and 89, respectively, are arcuate and are spaced from the pulley 47 byan appropriate distance that will maintain the cord 35 within the grooveof the pulley above the free ends '36 and 87 which hang down between theends 91 and 92 of the blocks 38 and 89.

There is a plate 95 pivotally attached with the block assembly 33, 89 bya rivet or the like 96 to the end cover plate 33. The cover plate 95 hasan upper surface 97 that includes an arcuate portion 98 of slightly lessradius than the radius of the arcuate surfaces 93 and 94 of the blocks88 and 8?. The edge )9 of the cover plate 95 is approximately contiguouswith the lower edges of the blocks 88 and '89. There is a bent plate 1%riveted to the cover plate 33 with a free end 1% spaced from the coverplate 33. The end 132 of the plate 95 opposite the rivet 96 fits betweenthe end 131 of the plate 1% and the cover plate 33. A leaf spring 193riveted to the cover plate 33 resiliently resists downward pivotingmovement of the free end 162 of the cover plate 95.

Secured to the cover plate 95 by means of the screws 93 is another leafspring which is considerably wider than the space between the ends 31and 532 of the blocks 88 and 89, and the lower free end 1% of the leafspring 1&5 is headed. The free end 166 of the leaf spring 1% is biasedtoward the cover plate 33 and tends to press the free ends 86 and 87 ofthe cord 85 against the end plate 33. The holding pressure of the leafspring 195 is greater than the force resulting from the weight of theslats 65 depending from the drum 54.

The way that the Venetian blind thus far described is operated, involvesthe manipulation of only a single cord 85 to both raise and lower theslats 65 and also to pivot them between an open and closed condition, aswell as various conditions therebetween. Assuming that the blind is allthe way down, as illustrated in FIGURES 1 and 18, the free ends 86 andS7 or" the cord 85 will be hanging fairly straight, as illustrated inFIGURE 12. The condition of the thin cords 7t 71 and 72 of the slats 65will be as illustrated in FIGURE 18. In this condition, the Venetianblind is open. That is, the slats 65 are horizontal and will obstructvery little vision through a window opening. The fine cords 70, 71 and72 are also practically invisible.

When it is desired to close or partially close the slats 65, they mustbe pivoted so that they assume positions tending toward a verticalplane. The only required action is that a force be applied to one of thefree ends 85 or 87 of the cord 85. When one of those free ends ispulled, the drum that is attached to the pulley 47 will be rotated. Uponrotation of the drum 54, as for example in a clockwise direction asviewed in FIGURE 20, the free ends 713 will be raised somewhat while theother free ends 71 will be slightly lowered upon initial rotation of thedrum 5 1. This condition of the cords 719 and 71 will cause the shortcord pieces 74 to be slanted, slanting with them the slats 65 that theysupport. The result is a partial closing of the Venetian blind uponpulling on one of the free ends 86 or 87 of the cord 85. During thisaction, the center cords 73 keep the slats 65 from slidinglongitudinally.

If the other of the free ends 86 or 87 is pulled so that the drum isrotated in a counterclockwise direction as viewed in FIGURE 19, the cord71 would be the one that would be raised while the cord 70 would belowered slightly. This action would cause the slats 65 to slant in theopposite direction.

Once either of the free ends 86 or 87 of the cord 85 has been pulled sothat an opposing load on the drum 54 is exerted by the weight of theslats 65 tending to unwind the drums 54, this opposing load will beresisted in part by the force of the leaf spring 1115. The leaf spring195 arrests the sliding of the free ends 85 and 87, and, once arrested,the drum 54 will reverse its rotation (a slight amount) in response tothe opposing force of the weight of the slats 65 causing the cord 56 or87 (whichever had een pulled) to become bunched between the leaf spring155 and the pulley :7. This bunching of the cord can be seen in FIGURE14. The bunching of the cord further crimps the space between the ends91 and 132 of the blocks 83 and 8% so that an additional locking effectis produced against the unwinding tendency of the weight of the Venetianblind.

When further rotation of the drum 54 is desired, either to further closethe slats 65 or to raise them by winding them about the drum 54, thefree end 87 is again pulled downwardly. Such pulling on the free endwill release the bunching part of the cord and cause the drum to berotated under the pulling force.

Each time the free cord end 87 is released, the locked effect abovedescribed will take place. It can be understood, therefore, that theblinds are raised or lowered or opened or closed by the action of thesingle cord 85.

FIGURE 21 is a single fragmentary view of a modification of theinvention wherein all of the slats 65 are cemented or otherwise attachedflatwise to a plurality of tapes 110. The uppermost slat is attached bycords 111 to the drum 54, the cords 111 in turn being taped by tapes 112to the drum 54. In this embodiment, when the cord 35 is pulled the drum54 will rotate and raise or lower the slats 65. The slats 65 cannot beopened and closed. The means for locking the cord 85 in the embodimentof FIGURE 21 is the same as that previously described.

FIGURES 22 through 28 represent another modification of the invention.This modification is directed particularly toward changes in the meansfor locking the cord except when pulled, and for attachment of the cords7t and 71 to the drum 54.

Referring to FIGURES 22, 23 and 24, there is an irregularly shapedcasting having arcuate wings 121 and 122 spaced from the pulley 47 anappropriate distance to retain the cord 85 within the groove of thepulley. The lower ends 123 and 124- of the arcuate wings 121 and 122 arespaced apart by a distance somewhat greater than double the diameter or"the cord 85.

The wings 121 and 122 merge into a bracket member 125 having flanges 126and 127 flat against the end cover plate 33. The bracket member 125 issecured to the end plate 33 by strips or" metal 128 and 129 bent outfrom the plate 33 and against the flanges 126 and 127. As can be seenfrom FEGURE 23, the flanges 126 and 127 have portions 13-19 and 131overlying the metal strips 128 and 129 so that the bracket will notslide from between the strips 125 and 129 and the plate 33. The centralportion of the bracket 125 is bent outwardly to provide an inner wall132 and side walls 133 and 134. The distance between the side walls 133and 134 is about the same as the distance between the lower ends 123 and124 of the arcuate wings 121 and 122. Also, the space between the innerside 132 and the plate 33 is somewhat greater than the diameter of thecord 35.

There is an inwardly directed bead 135 from each of the walls 132, 133and 134 so that when the free ends 86 and 87 of the cord 85 extendthrough the bracket 125 at the bead 135, they are restricted fromsliding by the bead 135. In other words, the bead 135 slightlycompresses the cord 85. When the weight of the Venetian blind is on thedrum 54-, the free end 86 or 87 will bunch within the walls 132, 133 or134 above the bead 135 in the same manner as the bunching occurs abovethe leaf spring 1115 with the first embodiment described.

The bracket 125 is attached to the plate 33 by first sliding the flange126 between the metal flaps 128 and the plate 33. If the bracket 125 isslanted far enough to the left as viewed in FIGURE 23, the flange 127can be shifted upwardly into the space between the flap 139 and theplate 33. V-Ihen the bracket 125 is then slanted part of the way backtoward the right, the overlying portions 139 and 131 will prevent thebracket from slipping away.

In PTGURES 25 through 28, the modified means for attaching the cords 7t?and 71 is illustrated. In this form of the invention there is a hole 149punched through the drum 54 for the cord 71) and another hole 141 forthe cord '71. The distance between the holes 140 and 141 isapproximately equal to the width of a slat 65.

To each of the cords is fastened a clip 142 that has a part 14-5 cutaway and bent over upon itself. The clip 142 is attached to the cord byfirst inserting the cord over the top of it in its unfolded formillustrated in FIGURE 28. The clip 14-2 is then bent tightly about thecord as illustrated in FIGURE 27. The bent over portion 143 eliminates asharp edge where the cord is bent.

The clip is held co-axially about the cord 70 and passed through thehole 148. The clip is then released so that it will assume a positionsubstantially perpendicular to the cord 35 so that it cannot slip out ofthe hole 140.

PTGURES 29 through 33 illustrate a still further modification of theinvention wherein a pair of Venetian blinds are mounted in substantiallysuperposed relationship so that the blinds can be used to effect a cafecurtain appearance. This arrangement also permits the complete coveringof a window by the Venetian blinds and then the opening of only one ofthe Venetian blinds, leaving the other closed. in this embodiment theupper of the Venetian blinds has been designated by prime numberscorresponding to the numbers already mentioned. Thus, in FIGURE 29, theupper and lower slats 65' and 65 are both fully lowered, completelycovering the window. In

FIGURE 30, only the upper slats 65 are lowered While the lower slats 65are completely raised. In FIGURE 31 the lower slats 65 are completelylowered while the upper slats 65' are completely hidden behind the cover39. In FIGURE 32 the lower slats 65 are completely lowered while theupper slats 65' are only partially lowered. Any number of variations arepossible with two Venetian blinds arranged as those in FIGURES 29-33.

Various changes and modifications may be made within the process of thisinvention as will be readily apparent to those skilled in the art. Suchchanges and modifications are within the scope and teaching of thisinvention as defined by the claims appended hereto.

What is claimed is:

1. A blind structure comprising a pair of brackets for attachment to awall, a drum rotatably supported between the brackets, a plurality ofpairs of cords suspended from the drum, a plurality of slats supportedbetween the cords of each pair, a pulley connected to one end of thedrum, a cord with a portion forming a loop hung over the pulley torotate the pulley and the drum in opposite directions, guide meanshaving arcuate surfaces beneath the pulley and close enough thereto tokeep the cord within the confines of the pulley, the arcuate surfaceshaving a space between them opposite the lowermost extreme of the pulleyand the cord having cord parts depending from the loop and extendingthrough the space, the width of the space being substantially greaterthan the combined diameter of the cord parts, but being substantiallyless than the diameter of the pulley, and means beneath the spacedefining a restricted passage through which the cord parts pass, therestricted passage having opposite sides that are closer together thanthe diameter of the cord parts so as to compress the cord parts andprovide an impedance to the passage of the cord parts through therestricted passage, the space above the restricted passage having sidewalls that extend far enough toward the restricted passage to preventescape of the cord parts beyond the lateral confines of the space, thecompressive force exerted by the restricted passage being sufiicientlygreat to cause bunching of the slack cord part when the slats areraised, the bunched cord part thereby providing a wedging block abovethe restricted passage of greater strength than the gravitational forcetending to lower the slats.

2. The blind of claim 1 wherein the flexible means comprise pairs ofsmall-diameter twisted fiber cord.

3. The combination ofclaim 1 wherein there are means for fastening theguide means and the means defining the restricted passage to one of thebrackets and wherein G the fastening means provide for the release ofthese parts from their operating positions defined herein.

4. The combination of claim 1 wherein the brackets are larger in surfacearea than the side to the drum and slats combined when all the slats arerolled about the drum, and a hood fastened to the edges of the bracketsand extending across the front of the drum above and below the uppermostand lowermost extremes of the slats when they are rolled about the drum.

5. The combination of claim 4 wherein the hood also extends across thetop of the drum and slats with the juncture between the front and topextensions being curved.

6. A Venetian blind comprising an elongated member, a pair of bracketsfor attachment to a mounting surface, means for mounting the member forrotation between the brackets, an elongated cord having a portion loopedabout the member for rotating it, with the cord parts adjacent the loophanging downwardly beneath the member, means defining the side Walls ofa restricted opening through which the hanging cord parts are drawn, theside Walls of the restricted opening including a leaf spring on one sideof the cord parts and a stop on the opposite side of the cord parts fromthe leaf spring, the restricted opening being positioned beneath themember but spaced from the member, a plurality of slats suspended fromthe member so that when one of the cord parts is pulled to rotate themember, the slats will be wrapped or unwrapped about the member, theleaf spring being continuously biased toward the cord parts so as toslightly compress the cord parts between the leaf spring and the stop,for thereby continuously applying a restraining force against movementof the other cord part when the one cord part is pulled, the magnitudeof the restraining force being greater than the weight of the slats.

References Cited in the tile of this patent UNITED STATES PATENTS 20,013Work c- Apr. 30, 1858 21,648 Bidwell Oct. 5, 1858 193,239 Fontayne July17, 1877 200,099 Stanley Feb. 5, 1878 203,418 Clark May 7, 18781,284,123 Masumian Nov. 5, 1918 2,111,978 Lawson et a1 Mar. 22, 19382,129,606 Nisenson Sept. 6, 1938 2,562,259 Burns July 31, 1951 2,723,715Kaufimann et al. Nov. 15, 1955 2,794,499 White June 4, 1957

1. A BLIND STRUCTURE COMPRISING A PAIR OF BRACKETS FOR ATTACHMENT TO AWALL, A DRUM ROTATABLY SUPPORTED BETWEEN THE BRACKETS, A PLURALITY OFPAIRS OF CORDS SUSPENDED FROM THE DRUM, A PLURALITY OF SLATS SUPPORTEDBETWEEN THE CORDS OF EACH PAIR, A PULLEY CONNECTED TO ONE END OF THEDRUM, A CORD WITH A PORTION FORMING A LOOP HUNG OVER THE PULLEY TOROTATE THE PULLEY AND THE DRUM IN OPPOSITE DIRECTIONS, GUIDE MEANSHAVING ARCUATE SURFACES BENEATH THE PULLEY AND CLOSE ENOUGH THERETO TOKEEP THE CORD WITHIN THE CONFINES OF THE PULLEY, THE ARCUATE SURFACESHAVING A SPACE BETWEEN THEM OPPOSITE THE LOWERMOST EXTREME OF THE PULLEYAND THE CORD HAVING CORD PARTS DEPENDING FROM THE LOOP AND EXTENDINGTHROUGH THE SPACE, THE WIDTH OF THE SPACE BEING SUBSTANTIALLY GREATERTHAN THE COMBINED DIAMETER OF THE CORD PARTS, BUT BEING SUBSTANTIALLYLESS THAN THE DIAMETER OF THE PULLEY, AND MEANS BENEATH THE SPACEDEFINING A RESTRICTED PASSAGE THROUGH WHICH THE CORD PARTS PASS, THERESTRICTED PASSAGE HAVING OPPOSITE SIDES THAT ARE CLOSER TOGETHER THANTHE DIAMETER OF THE CORD PARTS SO AS TO COMPRESS THE CORD PARTS ANDPROVIDE AN IMPEDANCE TO THE PASSAGE OF THE CORD PARTS THROUGH THERESTRICTED PASSAGE, THE SPACE ABOVE THE RESTRICTED PASSAGE HAVING SIDEWALLS THAT EXTEND FAR ENOUGH TOWARD THE RESTRICTED PASSAGE TO PREVENTESCAPE OF THE CORD PARTS BEYOND THE LATERAL CONFINES OF THE SPACE, THECOMPRESSIVE FORCE EXERTED BY THE RESTRICTED PASSAGE BEING SUFFICIENTLYGREAT TO CAUSE BUNCHING OF THE SLACK CORD PART WHEN THE SLATS ARERAISED, THE BUNCHED CORD PART THEREBY PROVIDING A WEDGING BLOCK ABOVETHE RESTRICTED PASSAGE OF GREATER STRENGTH THAN THE GRAVITATIONAL FORCETENDING TO LOWER THE SLATS.